By Peter Sousounis | January 2, 2020

Blog post illustration

As an In Focus reader you’ve probably read our climate change–related posts about floods, cyclones, winter storms, arctic acceleration, wildfire, and IPCC activities. While our models have been developed to reflect the current climate—accounting for the changes that have already occurred—as AIR’s first ever Director of Climate Change Research, I am responsible for identifying the research we must undertake to ensure that AIR’s catastrophe models continue to reflect the current climate as it changes.

Many of our models—such as U.S. wildfire and inland flood, European flood and extratropical cyclone, Australia bushfire, and Japan inland flood—leverage the last 40 years of observational and reanalysis data. Forty years is both a short enough period of time to limit biases from older data that may represent a climate that no longer exists and a long enough period of time to capture good representation of interannual variability. It is reasonable to ask, however, whether all 40 years’ worth of data should be weighted equally and whether using even longer periods of record, as we do for our tropical cyclone models, allows us to reflect the current climate without bias.

Due Diligence

Conducting the research and deciding how to use it is one part of my responsibility; another part is to perform due diligence on the historical data, look for any trends, determine whether or how significant they are, and then discuss with the model development teams how best to handle them.

As each model is updated, we perform a thorough historical trend analysis and determine how to weight the data. The results from the analyses and any trends that were accounted for become part of the documentation released with each model.

I’ve shared a few trends that were revealed through this type of analysis in recent blogs about Tropical Storm Imelda and the apparent slowing of tropical cyclones, how climate change may have made Typhoon Hagibis worse,  how wildfires in the Arctic can cause floods in the UK ,  and others. I’ve looked at significant increases in the proportion of strong winter cyclones affecting the eastern U.S., significant increases in Diablo and Santa Ana Winds in California, and significant increases in at least the potential for severe (convective) thunderstorms, especially over the eastern third of the United States.

Looking Ahead

A catastrophe model that reflects the current climate will certainly help clients manage their risk today, but planning for future changes to the climate is clearly a concern. Our client survey on climate change conducted last year indicated an interest in time horizons as far out as 50 years. Efforts to satisfy interest in these time horizons and beyond are already under way. Last year AIR responded to a request from the Prudential Regulatory Authority (PRA) to provide estimates of the impact to annual aggregate loss and 100-year return period losses for about 10 different climate change scenarios, including some for U.S. hurricane (and storm surge) and for UK extratropical cyclones.

Other industries and sectors such as urban planners, local governments, investors, and banks also need such tools. To address their needs, we are in the process of considering additional products and tools we can develop that will help our clients manage their risk and better prepare mitigation/adaptation strategies.

As our activities in the area of climate change pick up in 2020, we will be increasing the amount of engaging, collaborative research we conduct with individuals and organizations … and I will keep you posted.


Explore the sensitivity of catastrophe risk to a changing climate.



Categories: Climate Change

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